1. Field of the Invention
The present invention relates generally to down hole operations performed in wellbores and, more particularly, to the use of a vibrational source, such as an orbital mass vibrator, for performing such down hole operations.
2. State of the Art
Boreholes or wellbores are conventionally drilled from surface locations into hydrocarbon-bearing subterranean geological formations in order to obtain hydrocarbons such as oil and gas.
Often, during the drilling of a wellbore, the drill pipe utilized for drilling the wellbore gets stuck down hole, frequently at great distances from the surface location. Additionally, during completion, production and workover of the wellbores, tubing and various devices carried thereby get stuck that must be retrieved from the wellbore. In many cases the stuck object must be freed so as to further deploy the object within the wellbore, or so as to retrieve the object from the wellbore and continue with the attendant drilling, completion, production or workover operation.
A variety of methods have been utilized to free and retrieve stuck objects in wellbores in the oil and gas industry. For example, U.S. Pat. Nos. 4,913,234 and 4,667,742 issued to Bodine disclose the deployment of an orbital mass vibrator down hole to free a stuck pipe in a wellbore. The orbital vibrator of the 4,667,742 patent is mechanically coupled to an upper end of the stuck pipe in order to transfer vibrational energy thereto.
The orbital vibrator of the 4,913,234 patent likewise transfers energy to the stuck pipe in an effort to free it from the wellbore. However, the 4,913,234 patent teaches the transfer of energy by rotating the orbital vibrator precessionally around the inside wall of the of the stuck pipe. Thus, both of the above Bodine patents describe a process of freeing a stuck pipe which includes physical contact of the orbital vibrator with the stuck member.
Other operations performed in preparing a wellbore for the production of hydrocarbons likewise benefit from the use of a vibrational energy source. For example, upon deployment of a liner, or a tubular string down the well bore, cement is pumped down hole to fill the space (annulus) between the liner and the wellbore wall. During disposition of cement into the annulus, the liner may be vibrated to fill any voids or channels in the annulus, consolidate the cement and to generally improve the integrity of the cement bond between the liner and the wellbore. Other methods of removing voids in the cement have included deploying a down hole vibrational source during disposition of cement into the annulus.
For example, U.S. Pat. No. 5,515,918 to Brett et al. discloses deployment of an orbital mass vibrator down hole for transferring vibrational energy to a cement slurry. The 5,515,918 patent describes a vibrator which rotates a mass about a longitudinal axis in one direction to induce a backward xe2x80x9cwhirlxe2x80x9d of the mass in the opposite direction. However, the backward whirl of the orbital vibrator includes the mass contacting and precessionally rotating about the interior of the liner or other tubular in which the vibrator is disposed. Such contact may be undesirable in that inadvertent damage may occur to the liner or other tubular string.
U.S. Pat. No. 4,658,897 issued to Kompanek et al. discloses another method of inducing vibrational energy to a cement slurry. The 4,658,897 patent teaches the down hole deployment of a transducer system for transferring vibrational energy to the cement slurry. The transducer is drawn upwardly through the bore hole to eliminate pockets or voids in the slurry. However, such a method fails to teach the identification and isolation of voids or pockets within the cement slurry.
U.S. Pat. No. 6,009,948 issued to Flanders et al. discloses the use of a vibratory source for either freeing a stuck pipe or other object from the well bore or for aiding in cementing operations. The vibratory tool is deployed down hole and is engaged with an object to transfer vibrational energy thereto. With regard to freeing stuck pipes, the vibratory tool is stated to determine the optimum frequency (i.e., resonance) and the operate at that frequency. However, as noted above, the 6,009,948 patent still teaches the physical engagement or coupling of the vibratory source with the stuck pipe or object. Such physical coupling with the pipe or other object for purposes or transferring vibrational energy thereto (or therethrough) may result in unwanted stresses or strains in the pipe or object and may ultimately result in damage incurred by the object to which the vibrator is coupled.
In view of the shortcomings in the art, it would be advantageous to provide an apparatus and method for transferring vibrational energy to specific locations in the wellbore in association with performing various down hole operations. For example, it would be advantageous to provide an apparatus and method which allowed the freeing of stuck tubulars or like objects without mechanically and physically coupling the vibrational source to the stuck object.
Likewise, it would be advantageous to provide an apparatus and method for identifying specific locations of voids or pockets in a cement slurry, and then applying appropriate levels of vibrational energy to those locations for removal of such voids or pockets.
In accordance with one aspect of the invention, a method of inducing vibrational energy in a tubular member is provided. The method includes deploying a vibrational source within an interior portion of the tubular member. A fluid medium is disposed within an annulus formed between the vibrational source and an interior surface of the tubular member. The vibrational source is operated using the fluid medium to create a fluid coupling between the vibrational source and the tubular member. The fluid medium may be a fluid already present in the tubular member, such as, for example, drilling mud. Alternatively the fluid medium may be disposed in the tubular member specifically for the particular task of forming a fluid coupling with the tubular member.
In accordance with another aspect of the present invention, a method of freeing a stuck tubular from a wellbore is provided. The method includes disposing a vibrational source within the stuck tubular adjacent a point of sticking. A fluid coupling is formed between the vibrational source and the stock tubular using a fluid medium disposed within the stuck tubular to transfer vibrational energy from the vibrational source to the stuck tubular and reducing friction between the stuck tubular and the wellbore.
In accordance with another aspect of the present invention, a method is provided for cementing a wellbore. The method includes inserting a tubular member within the well bore so as to define a first outer annulus between the wellbore wall and an exterior surface of the tubular member and cement slurry is disposed into the first outer annulus. A vibrational source is disposed within the tubular member so as to define a second inner annulus between an exterior portion of the vibrational source and an interior surface of the tubular member. A fluid coupling is formed between the vibrational source and the tubular member using a fluid medium disposed in the second annulus to transfer vibrational energy to and through the tubular member and into the cement slurry disposed in the first outer annulus.